1. Field of the Invention
This invention relates to a thread take-up lever device for sewing machines and particularly to improvements for enhancing the performance of the thread take-up lever itself included in a thread take-up lever device.
2. Description of the Prior Art
In the most common sewing machine, the tread take-up lever has an eyelet. And an upper thread is passed through said eyelet. In operative association With an upper shaft or main shaft housed in a sewing machine frame and driven for rotation, the thread take-up lever is vertically reciprocated and in accordance with this reciprocating motion it tightens or loosens the thread by the amount necessary for forming a stitch.
It is usual for the thread take-up lever to be reciprocated in a vertically extending slit formed in the frame. In the sewing machine of the type described above, to make possible an operation for passing a thread through the eyelet of the thread take-up lever, a state in which the eyelet comes out of the frame must be created over at least a portion of the range of reciprocating motion of the thread take-up lever. For this reason, it has been impossible to house the thread take-up lever completely in the frame.
On the other hand, an eyeletless thread take-up lever is disclosed in U.S. Pat. No. 3,782,312 granted to Kasuga on Jan. 1, 1974. According to this patent, the thread take-up lever is formed with a hook portion adapted to engage the thread when drawing the latter. Thus, the operation for passing the thread through an eyelet becomes unnecessary and hence the thread take-up lever can be completely housed without being exposed outside the frame.
A thread take-up lever functions to tighten or loosen the thread in accordance with its reciprocating motion. In this connection, it is to be noted that because of its tightening action on the thread, the thread take-up lever often causes thread breaks. On such occasions, the thread suddenly loosens and clings to the thread take-up lever and in extreme cases it coils itself around the thread take-up lever in cooperation with the movement of the thread take-up lever. In the case where the thread clings to or coils itself around the thread take-up lever, it is very difficult to undo this condition, and particularly in a sewing machine of the type in which the thread take-up lever is housed completely in the frame, it is not an easy job to undo the clinging or coiling of the thread to or around the thread take-up lever.
Further, the occasion of the thread clinging to or coiling around the thread take-up lever is not limited to the time when a thread break takes place. Such clinging to the thread take-up lever may occur very often depending upon the kind of the thread even during normal operation of the sewing machine. For example, in the case of a fluffy thread or a hard-twist thread, such clinging phenomena would be noticeable.